Tamerlan Tsarnaev’s name was entered into the Treasury Enforcement Communications System, or TECS, as a routine procedure when the FBI looked into whether Tsarnaev was involved in terrorist activity, the law enforcement officials said, speaking on condition of anonymity because the investigation was ongoing. TECS is the system used by U.S. officials at the nation’s borders to help screen people arriving in the U.S. …

According to one of the officials, an airline misspelled Tsarnaev’s name when it submitted the list of passengers on Tsarnaev’s flight to Russia in January 2012. Airlines are required to provide the U.S. government with a list of passengers on international flights so the U.S. can check their names through government databases, including the terrorist watch list.

But because Tsarnaev’s name was misspelled, it was not matched with the 2011 entry in the TECS system, the official told the AP. However, the official said, even if his name had been spelled correctly and U.S. officials recognized that Tsarnaev, the subject of a 2011 FBI inquiry, was on the flight, he would have faced no additional scrutiny because the FBI had by that time found no information connecting Tsarnaev to terrorism.